Chapter 4: Sensation and Perception Vision: The Stimulus Light = electromagnetic radiation Amplitude: perception of brightness Wavelength: perception of color Purity: mix of wavelengths perception of saturation, or richness of colors. The Eye: A Living Optical Instrument The eye: housing and channeling Components: Cornea: where light enters the eye Lens: focuses the light rays on the retina Iris: colored ring of muscle, constricts or dilates via amount of light Pupil: regulates amount of light Figure 4.2 The human eye The Retina: The Brain?s Envoy in the Eye Retina: absorbs light, processes images Optic disk: optic nerve connection/blind spot Receptor cells: Rods: black and white/low light vision Cones: color and daylight vision